1. Field
The present application relates to a high-density storage rack for storing nuclear fuel assemblies before or after using thereinto, and more particularly, to a suspension type high-density storage rack for nuclear fuel assemblies that has each nuclear fuel assembly suspended from a cap part adapted to be coupled to the upper portion of each of a plurality of basket cells, such that the nuclear fuel assemblies are placed correspondingly inside the basket cells, thereby preventing their internal deformation caused by their own weight thereof.
2. Background of the Related Art
Generally, the nuclear fuel assemblies before using in a nuclear power plant are stored in a storage rack, and then, the storage rack is fixed by means of bolts to a storage tank in a fuel building, such that the nuclear fuel assemblies are stored in the air. Contrarily, the nuclear fuel assemblies after using are stored in the storage rack and freely supported in the water into the storage tank in the fuel building.
One example of conventional storage racks is disclosed in Korean Patent Laid-Open Publication No. 10-2005-0001744 entitled ‘low-density storage rack for nuclear fuel assemblies in nuclear power plant’.
The above-mentioned prior art suggests a nuclear fuel assembly storage rack adapted to support a square lattice structure made of stainless steel and a poison box to store the nuclear fuel assembly therein by means of a support bar, wherein the welded portion having a length of 4.5 inches between the square lattice-structured cans in the nuclear fuel assembly storage rack is divided into five equally-spaced sections.
According to the above-mentioned prior art, the generation of bad welded portions caused when the square lattice-structured cans are welded to each other is reduced, thereby decreasing the time and personnel cost consumed for the welding. However, it is disadvantageous that the number of nuclear fuel assemblies stored in the storage rack is less than the number of square lattice-structured cans.
To solve the above-mentioned problems, recently, there is provided a storage rack using a neutron absorber to increase a storage capacity for nuclear fuel assemblies. The neutron absorber is made of borated stainless steel, Boraflex, boarl, or the like. The storage rack is called a high-density storage rack, which has the neutron absorber adapted to decrease the distance between the nuclear fuel assemblies for maintaining a subcritical state, thereby increasing the storage capacity of the nuclear fuel assemblies.
One example of the conventional storage racks having the neutron absorber is disclosed in Japanese Patent Laid-Open Publication No. 11(1999)-0014785 entitled ‘a storage rack for nuclear fuel assemblies and method for manufacturing the same’.
According to the above-mentioned Japanese prior art, the storage rack for nuclear fuel assemblies has the following advantages: first, the storage rack has a storage capacity for storing a relatively large number of nuclear fuel assemblies in a given volume; second, it is not changed to a critical state; third, it is easy to make it; and fourth, a relatively low manufacturing cost is needed.
The conventional storage rack for the nuclear fuel assemblies has a plurality of housings regularly arranged therein, each housing having a plurality of main plates and a plurality of spacer plates and a base plate, wherein protruding parts formed on two lengthwise edges of the spacer plates are inserted in housing holes of the main plates such that the main plates and the spacer plates are fixed to each other by means of mechanical insertion.
However, since the conventional storage rack stores the nuclear fuel assemblies at a state of being erected on the lower end inside the square tubes, the nuclear fuel assemblies are finely inclined to a predetermined angle in the interior of the square tubes, thereby causing their eccentricity. More particularly, if the nuclear fuel assemblies are stored for a long period of time, they become eccentric to finally cause their internal deformation by their own weight.
On the other hand, if the deformed nuclear fuel assemblies (that is, fresh nuclear fuel) before using are mounted in a nuclear reactor core, unexpected problems will occur.